Fuel pump for internal combustion engines



March 18, 1941. R TmER 2,235,052

FUEL PUMP FOR INTERNAL COMBUSTION ENGINES Filed June 9, 1959 ntentedMar. 18, 1941 NITED STATES FUEL PUMP FOR INTERNAL COMBUSTION ENGINESPaul W. Trier, Detroit, Mich, assignor to Briggs & Stratton Corporation,Milwaukee, Wis., a corporation of Delaware Application June 9, 1939,Serial No. 278,186

2 Claims.

This invention relates to pumps, and refers particularly to fuel pumpsfor internal combustion engines.

Fuel pumps now in general use embody a reciprocating pumping memberwhich draws fuel into a pump chamber during one stroke and expels itduring the other stroke. This construction entails the use of checkvalves, which often do not operate properly, particularly when vapordevelops inside the pump. This latter condition is known to the art as avapor lock.

The present invention proposes to overcome the objections incident to apump structure subject to the development of vapor locks, andaccomplishes this object through the provision of a continuouslyrotating feed screw which propels the liquid forwardly as long as ademand exists, and which is so constructed as to permit slippage in theevent of back pressure in excess of a predetermined amount.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed, and more particularly defined by the appended claims, itbeing understood that such changes in the precise embodi-' ment of theherein-disclosed invention may be made as come within the scope of theclaims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed in accordancewith thebest mode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a sectional view through a pump constructed in accordancewith this invention; and

) Figure 2 is a view similar to Figure 1, but showing the manner inwhich back pressure causes the liquid to slip past the pumping member.

Referring now particularly to the accompanying drawing in which likenumerals indicate like parts, the numeral 5 designates the body of thepump, which has a cylindrical bore 6 open at one end and closed at itsopposite end by a. wall I. The open end of the pump body, is fixed to anend plate 8 designed to close an aperture in the crankcase of the enginewith which it is used. 1

This end plate and the opposite end wall of the body have axiallyaligned bearings 9 and I0, respectively, in which a shaft I l isJournalled. The inner end of the shaft projects beyond the end plate 8to mount a pinion l2 by which the shaft is driven from any suitablepower source inside the crankcase (not shown).

At one end. the pump body has an inlet I3 leading to its bore 8 and atits opposite end, an outlet It leads from the bore 6. Liquid isprogelled through the bore 8 from the inlet to the outlet by a screw l5mounted on the shaft H to be rotated thereby. The screw I5 is formed'ofrubber, or other similar material having cubical elasticity, and itsnormal shape is such that its peripheral edge It has a firm engagementwith the bore 6 to provide a fluid tight seal capable of creating asuction in the inlet end of the body to draw liquid fuel into it andpropel it to the outlet M.

The resiliency of the rubber screw allows it to flex, as shown in Figure2, whenever back pressure, indicated by the dotted arrows in Figure 2,exceeds a predetermined value. In this manner, the liquid is allowed toslip past the ,vanes of the screw so that the output of the pump isresponsive solely to the demands of the carburetor.

From the foregoing description takenin connection with the accompanyingdrawing, it will be'readily apparent that this invention effects asubstantial improvement in pumps designed for use in feeding fuel to thecarburetors of internal combustion engines as it eliminates thepossibility of vapor locks.

What I claim as my invention is:

1. A pump comprising: a body having a bore provided with longitudinallyspaced inlet and outlet openings: and a rubber screw rotatable in thebore and having a convolution of a diameter such that its periphery isnormally held in fluid tight engagement with the wall of the bore so asto propel liquids from the inlet to the outlet upon rotation of thescrew in one direction in said bore, the thickness of. said convolutionbeing substantially less than its height whereby the convolution isrendered flexible to permit flexure thereof out of engagement with thewall of the bore whenever back pressure in the pump body exceedsapredetermined value.

2. In a pump of the character described: a body having a substantiallycylindrical fluid passageway; and a screw rotatable in said passagewayfor propelling" fluids therethrough, said screw having a. convolution ofnon-metallic material capable of substantial deflection withoutdeformation and of a diameter such that its periphery normally engagesthe wall of the passageway in fluid tight relationship therewith toproduce a pressure below a predetermined value during rotation of thescrew in the passageway, the thickness of said convolution beingsubstantially less than its height whereby the convolution is renderedflexible to permit the same to be flexed out of fluid tight relationshipwith the wall of the passageway when resisted by a fluid pressure insaid passageway above said predetermined value.

PAUL W. TRIER.

